Skip to content

Demucs - API

We provide a REST API to programmatically make requests to the service.

The API endpoint is:

API service

The API runs on Google Cloud Run and you can read about our implementation here.

Predict endpoint

The /predict is a POST endpoint that receives a JSON object in the body.

The endpoint received a base64 encoded versions of a song.

  • The JSON body object should have one item called instances which contains a list of child objects
  • The child object should contain one item called b64
  • The value of b64 should be a base64 encoded version of the song.

And example request body would be as follows:

  "instances": [
      "b64": "SUQzBAAAAAACfFRYWFg[...]"

The response will also be JSON object containing 4 base64 encoded mp3 songs in a similar format:

    "drums": "[... base64 string ...]",
    "bass": "[... base64 string ...]",
    "other": "[... base64 string ...]",
    "vocals": "[... base64 string ...]"


The API has an OpenAPI UI that can be acceded at the /docs endpoint:

From here is also possible to test the API.

Postman Collection

We provide a Postman Collection with a small 3 second mix fragment to test the API. Access it here: Demucs postman collection.

Base64 encode an mp3 file

You can easily convert an .mp3 file to base64 using this command:

base64 mixture.mp3 > mixture.b64.txt